Friday, August 26, 2016

This is a clarification of how trebuchets are measured for classification in the different weight divisions: lightweight, middleweight, and heavyweight. See the official rules for specifications.

The height of the trebuchet is the difference between the top and bottom.

The top is the highest point reached by the arm (including the finger) or the counterweight (CW) during firing. The bottom is the lowest point of the arm or counterweight during firing.

For a King Arthur trebuchet two measurements are made when the trebuchet is at rest; the highest point of the finger and the lowest point of the counterweight. Two measurements are made when the treb is loaded; the highest point of the counterweight and the lowest point of the finger. See figures 1 and 2.

All four measurements are made from a convenient fixed level; the ground is a good level or the lowest point of the trebuchet.

The four measurements are:

Highest point of finger at rest

Lowest point of CW at rest

Lowest point of finger when loaded

Highest point of CW when loaded

The top is the highest of all four points and the bottom is the lowest of all four points. So the height of the trebuchet is simply the distance between the highest top and the lowest bottom.

See figures 3 and 4 for a floating point trebuchet measurements.

If you have any questions please contact the event organizer, Dave Jordan.

Saturday, August 6, 2016

There are now only 50 days until the 8th Annual Vermont Pumpkin Cuckin' Festival on Sept. 25th, 2016.
Time to get down to business and get your machines dialed in. In the meantime here are some hurling items that caught out eye:

There is an interesting article discussing trebuchets at Slate.com from Quora. It does have one error when it states:

Trebuchets, because they don’t recoil in the same way as catapults, can be put on wheels. In fact, doing so is advantageous for their accuracy, as I understand it, because of the way it lets the whole machine absorb some of the forces involved.

A trebuchet on wheels loses distance on its throws. The wheels rob the full transfer of energy from the counter-weight to the throwing arm. A trebuchet should be anchored to the ground to be most efficient. There is no real debate about that. Wheels would probably make it easier to line up a trebuchet, but taking time and adjusting a grounded trebuchet will make it just as accurate, plus it will have more distance, than a wheeled version.

A trebuchet is a device for attacking fortifications. Roughly speaking, a trebuchet has a few advantages over a catapult. First, it can handle heavier projectiles. A catapult’s maximum weight tops out at about 180 pounds; trebuchets top out at about 350. Second, compared with a torsion engine, it’s a fairly robust machine. Lastly, for a given weight of stone, the trebuchet has a longer range. The big ones there, of course, are the maximum projectile weight and range. When your objective is to smash stone fortifications, being able to throw bigger stones from farther away is certainly a desirable trait...

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This Game of Thrones trebuchet looks good, but it has several problems as Scott Manning points out.

Yes, I’m critiquing the plausibility of this trebuchet while ignoring the dragons.

The “Battle of the Bastards” episode from Game of Thrones introduced a new twist on the trebuchet, utilizing gravity but defying physics and logic.

It was in the background of the siege of Meereen. Blink and you’ll miss it.

Like a trebuchet, the machine utilizes gravity to propel an object toward a target. However, there are some major problems with this machine.

1.) The counterweight just isn’t enough

Instead of a traditional counterweight, there is a mini-rollercoaster that sends the entire arm down before flinging it forward. This is an adoption of a modern design affectionately named Merlin (thanks to Son_of_mogh for pointing this out)...

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How about a quick history lesson with some art thrown in (pun intended)?

Boris undergoing repairs. The trebuchet at Our Farm needed to have its throwing arm replaced after it cracked. Courtesy Our Farm.

Boris the trebuchet got a “heart transplant” recently at the Golub family’s Our Farm on Peth Road in Cazenovia/Manlius — and now the 10-year-old pumpkin launching machine is ready to keep on chucking fruit for a long time to come...